A invention relates to a switch-over device, preferably usable for a gas insufflation device using liquid gas, having at least two inflow channels, each blockable by a valve and at least one outflow channel for alternate removal of a fluid medium from a plurality of containers, and having a switch-over piston movably mounted in a housing and comprising a base member which has at each end a valve closure member in the form of a body of rotation, this switch-over piston being driven by a pressure difference between the flulid media and connecting one of the inflow channels to the outflow channel in each of two switching positions, and with a working chamber which accommodates the switch-over piston, sealing elements being provided for closing off the inflow channels in a pressure-tight manner when the switch-over piston is in the correspondingly closed position and for dividing the working chamber into two portions sealed off from each other.
Switch-over devices for equipment are known which operate with a pressure medium which can be removed from a plurality of pressurised containers, for example a gas from gas bottles. The switch-over device provided ensures that a pressurised container which has been emptied, apart from a certain residue, is disconnected from the plant system and at the same time a full pressurised container is connected up without interrupting the operation of the plant system.
From German patent 29 18 791, a switch-over device is known with which it is possible to remove a pressurised liquid or gaseous medium from batteries of bottle cells or containers in alternating manner. The switch-over device comprises two valve-controlled inlet channels and one outlet channel. Switching the outlet channel from one inlet channel to the other is effected by the fluid medium using a switch-over piston which has a valve closure member at each of its two ends. The corresponding valve seatings are arranged in a chamber which accommodates the switch-over piston within the housing of the switch-over device and are constructed as bushings have a ring seal. The valve closure member is formed by a pin which engages in the correspondingly shaped recess in the bushing when the valve is shut. The end face of the switch-over piston is supported simultaneously on the bushing which forms the valve seating. The fluid medium which brings about the switch-over applies pressure, at the end where the valve is open, to the entire and face of the switching piston, whereas at the end where the valve is closed, only the end face of the valve closure member is subjected to the entry pressure. The chamber which accommodates the switch-over piston is connected, at both ends of the switch-over piston, with a pressure relief valve by means of which the corresponding chamber area can release its pressure into the output line of the switch-over device which supplies the consumer.
The solution described above has the major disadvantage that the desired method of operation is ensured only for a specific flow medium and for given pressure conditions for the switch-over. The use of the switch-over device for a different flow medium and different switch-over conditions requires a different construction both of the switch-over piston and of the housing of the switch-over device.